The invention concerns a sintered film containing a copolymer and optionally other common additives.
The use of the so-called powder-slush-molding method has been known for some time for the production of interior coverings of motor vehicles, particularly for the production of instrument panels. Sintered films which are produced according to this method using a PVC powder are known. The PVC powder is thereby sintered together and gelled. With this process, neither additional pressure nor additional shearing are used.
In the powder-slush-molding method, referred to hereafter as the "slush" method, the following processing steps are carried out successively: heating the tool, PVC powder filling and rotating of the tool, gelling of the PVC, and cooling and releasing from the mold. In comparison to deep-drawn films, the products formed according to the slush method have the advantage of more extensive freedom from stress and a more flexible conformation. Moreover, with the slush process, a designer has greater freedom in shaping. PVC materials, like the PVC sintered films described above, are being rejected more and more with regard to environmental protection. Therefore, in German Patent No. 39 16 874 [Offenlegungsschrift] sintered films based on polyurethane were proposed, which are used in particular to coat shaped parts in the interior space of motor vehicles. If aromatic thermoplastic polyurethanes (TPU), possibly thermoplastic polyurethanes, are used according to this known proposal, such sintered films are not satisfactory with respect to the light resistance requirement of the automobile industry. Sintered films made of high-molecular-weight polyethylene in particular are known from German Patent No. 29 22 152 [Offenlegungsschrift]. They did not always fulfill the requirements for, for example, the interior coverings of motor vehicles, particularly the instrument-panel area. Special requirements that can be mentioned here are the following: a Shore A hardness of approximately 70 to 90, fogging properties of less than 1 mg according to DIN 75 201/g. and of more than 85% according to DIN 75 201/r, and a resistance to light of more than LE 7 according to DIN 75 202. This list is not exhaustive.
The object of the present invention is to prepare a sintered film based on a thermoplastic polyolefin which can be produced according to the slush method without problems, which fulfills the requirements stated above, and which is satisfactory with respect to environmental protection.